将K₂SO₄、Al₂(SO₄)₃两种盐混合于硫酸酸化的水中，测得c(SO₄^2－)＝0.03 mol/L，c(Al^3＋)＝0.005 mol/L，c(H^＋)＝0.01 mol/L(假设溶液中H₂SO₄完全电离为H^＋和SO₄^2－)，则c(K^＋)为

A．0.045 mol/L

B．0.035 mol/L

C．0.005 mol/L

D．0.040 mol/L